Apr 24 OPP: Ore Preparation Plants Explained

Once the oil sands is hauled out of the mine, the ore is first processed in an Ore Preparation Plant (OPP), where clumps of oil sands are broken down and mixed with hot/warm water to produce a pumpable slurry. OPP facilities have evolved considerably in recent years and provide a critical first step in the extraction of bitumen.

The Ore Preparation Plant (OPP) is the first step within any Bitumen Production facility where mined oil sands is loosely crushed and mixed with hot/warm water to form a slurry that can be pumped to the main processing plant. OPPs are divided into two sections: a dry side, where the oil sands is crushed, screened and stored, and a wet side, where a pumpable slurry is produced.

Ore preparation serves several important functions:

Breaking down the clumps: Mined oil sands can contain large chucks of bitumen, ice and fine solids. OPP breaks these clumps down into a loose, unconsolidated material that can be more effectively mixed with water.

Removal of oversized material: Aside from chunks of bitumen, mined oil sands can also contain large chunks of ice, petrified wood or even pieces of scrap metal. This oversized material can damage downstream equipment and is therefore removed from the slurry.

Surge capacity: Although mines operate 24/7, mining is a batch process susceptible to brief outages. Supply disruptions can occur when shovels are being relocated, during shift change and especially in spring when ground conditions are very soft. OPP provides critical surge capacity, allowing Bitumen Production to continue operation uninterrupted, at least for a few hours.

Slurrying and aeration: Hot/warm water is added to the oil sands, creating a pumpable slurry that can be pipelined to the Extraction plant. Vigorous mixing within OPP allows the slurry mixture to aerate and entrain air bubbles, a critical step in downstream bitumen recovery.

PROCESS OVERVIEW

OPP facilities consist of two separate sections, normally referred to as OPP-Dry (or Material Handling Plant) and OPP-Wet (or Slurry Preparation Plant). Although the equipment used and configurations vary among the operators, the basic steps in an OPP facility are as follows:

OPP-DRY:MATERIAL HANDLING PLANT

OPP-WET:SLURRY PREPARATION PLANT

Mined oil sands hauled to OPP and dumped into a hopper which feeds into double-roll crushers or sizers.

The crushers/sizers break up clumps of oil sands into loose sand and crush any oversize material, such as ice or petrified wood.

The crushed ore is dumped onto conveyors, which transport the loose oil sands to a storage pile or surge bin.

Hot or warm water is added to the oil sands and vigorously mixed to produce an aerated slurry.

Screens within the slurry preparation area remove any oversized material that might damage downstream equipment. This oversized material is either crushed and reprocessed or rejected.

Caustic soda can be added to the process water to raise the slurry pH to about 9. This helps improve bitumen recovery.

The oil sands slurry is then pipelined to Extraction in a process known as Hydrotransport.

LAYOUT CONSIDERATIONS

One of the biggest costs for any oil sands mine operator is the number of haul trucks and the volumes of diesel burned to move material from the mine to the processing plant. As a result, it is desired to minimize elevation changes and hauling distances that the mining trucks need to travel.

OPPs are normally built closer to the mine pit, which can sometimes be a considerable distance away from the processing plant. Since the oil sands ore is mined out of a pit (or hole in the ground), the crushing plant is normally also installed at a lower elevation, or in-pit. This helps minimize elevation changes for the haul trucks.

Slurry preparation plants are also typically located far away from the processing plant, somewhere between OPP-Dry and Extraction. This distance is critical to bitumen recovery within the Hydrotransport line.

OIL SANDS TRANSPORTATION FACTS:

When moving oil sands around the mine, consider the following cost hierarchy:

pipelines are cheaper than conveyors

conveyors are cheaper than trucks

trucks are by far the most expensive transportation method.

The Mine Plan and layout of OPP therefore always looks to minimize the hauling distance required for transport of oil sands ore and removal of overburden material. OPPs are therefore normally installed closer to the mine pit, sometimes several kilometers far away from the processing plant. In newer installations, mobile and semi-mobile crushing plants have become the norm. As the mine plan progresses, the material handling plants are relocated in tandem in order to shorten hauling distances.

THE NEXT STEP: HYDROTRANSPORT

The slurry produced in the Slurry Preparation Plant is pumped to Extraction through a series of large-diameter pipelines and heavy duty slurry pumps. These pipelines and pumps are termed Hydrotransport, providing critical time for addition mixing, aeration and break-down of oil sands lumps.